M.A. Psychologyhttp://hdl.handle.net/10464/2242
Tue, 31 Mar 2015 22:05:59 GMT2015-03-31T22:05:59ZDisambiguating the Effects of Social Instability Stress in Adolescence on Learning and Memory Tasks that Involve the Medial Prefrontal Cortex and Hippocampushttp://hdl.handle.net/10464/4646
Disambiguating the Effects of Social Instability Stress in Adolescence on Learning and Memory Tasks that Involve the Medial Prefrontal Cortex and Hippocampus
Green, Matthew
Exposure to chronic stress can alter the structure and function of brain regions involved in learning and memory, and these effects are typically long-lasting if the stress occurs during sensitive periods of development. Until recently, adolescence has received relatively little attention as a sensitive period of development, despite marked changes in behaviour, heightened reactivity to stressors, and cognitive and neural maturation. Therefore, the purpose of the present study was to investigate the long-term effects of chronic stress in adolescence on two spatial learning and memory tasks (Morris water maze and Spatial Object Location test) and on a working memory task (Delayed Alternation task). Male rats were randomly assigned to chronic social instability stress (SS; daily 1 hour isolation and subsequent change of cage partner between postnatal days 30 and 45) or to a no-stress control group (CTL). During acquisition learning in the Morris water maze task, SS rats demonstrated impaired long-term memory for the location of the hidden escape platform compared to CTL rats, although the impairment was only seen after the first day of training. Similarly, SS rats had impaired long-term memory in the Spatial Object Location test after a long delay (240 minutes), but not after shorter delays (15 or 60 minutes) compared to CTL rats. On the Delayed Alternation task, which assessed working memory across delays ranging from 5 to 90 seconds, no group differences were observed. These results are partially in line with previous research that revealed adult impairment on spatial learning and memory tasks after exposure to chronic social instability stress in adolescence. The observed deficits, however, appear to be limited to long-term memory as no group differences were observed during brief periods of retention.
Thu, 11 Jul 2013 00:00:00 GMThttp://hdl.handle.net/10464/46462013-07-11T00:00:00ZInvestigation of the Relationship between Sexual Orientation and Objective Height, along with Predictors of Height Distortionhttp://hdl.handle.net/10464/4362
Investigation of the Relationship between Sexual Orientation and Objective Height, along with Predictors of Height Distortion
Skorska, Malvina Nina
Studies that have used mostly self-reported height have found that men with a same-sex
orientation and women with an other-sex orientation are shorter, on average, than men
with an other-sex orientation and women with a same-sex orientation, respectively. This
thesis examined whether an objective height difference exists or whether a psychosocial
account (e.g., distortion of self-reports) may explain these putative height differences.
Also, this thesis examined whether certain individual differences (e.g, gender roles and
socially desirable responding) predict height distortion. Eight hundred and thirteen
participants, recruited at Brock University, the Niagara Community and through
surrounding LGBT events, completed self-reported height, measures of gender roles and
socially desirable responding, and had their height measured. Using hierarchical linear
regressions, it was found that Same-Sex/Both-Sex Oriented men were shorter, on
average, than predominantly Other-Sex Oriented men; however, there was no difference
in objective height between Same-Sex/Both-Sex Oriented women and predominantly
Other-Sex Oriented women. These findings contribute to existing biological theories of
men's sexual orientation development and do not contribute to biological theories of
women's sexual orientation development. Height distortion was not related to sexual
orientation and only marginally related to sex. Predictors of height distortion were
Impression Management, in both men and women, and Unmitigated Agency, in men.
These findings highlight the complexity of sexual orientation development in men and
women. These findings also highlight the role of certain psychosocial factors in how
people perceive their bodies and/or how they want their bodies to be perceived by others.
Tue, 07 May 2013 00:00:00 GMThttp://hdl.handle.net/10464/43622013-05-07T00:00:00ZForgiveness in Two Minds: Understanding Forgiveness Through Dual-Process Theoryhttp://hdl.handle.net/10464/4361
Forgiveness in Two Minds: Understanding Forgiveness Through Dual-Process Theory
Rubel, Alicia N.
In this thesis, I examined the relevance of dual-process theory to understanding
forgiveness. Specifically, I argued that the internal conflict experienced by laypersons
when forgiving (or finding themselves unable to forgive) and the discrepancies between
existing definitions of forgiveness can currently be best understood through the lens of
dual-process theory. Dual-process theory holds that individuals engage in two broad
forms of mental processing corresponding to two systems, here referred to as System 1
and System 2. System 1 processing is automatic, unconscious, and operates through
learned associations and heuristics. System 2 processing is effortful, conscious, and
operates through rule-based and hypothetical thinking. Different definitions of
forgiveness amongst both lay persons and scholars may reflect different processes within
each system. Further, lay experiences with internal conflict concerning forgiveness may
frequently result from processes within each system leading to different cognitive,
affective, and behavioural responses. The study conducted for this thesis tested the
hypotheses that processing within System 1 can directly affect one's likelihood to
forgive, and that this effect is moderated by System 2 processing. I used subliminal
conditioning to manipulate System 1 processing by creating positive or negative
conditioned attitudes towards a hypothetical transgressor. I used working memory load
(WML) to inhibit System 2 processing amongst half of the participants. The conditioning
phase of the study failed and so no conclusions could be drawn regarding the roles of
System 1 and System 2 in forgiveness. The implications of dual-process theory for
forgiveness research and clinical practice, and directions for future research are
discussed.
Tue, 07 May 2013 00:00:00 GMThttp://hdl.handle.net/10464/43612013-05-07T00:00:00ZFrontal Lobe Function and Performance Monitoring following Total Sleep Deprivationhttp://hdl.handle.net/10464/4360
Frontal Lobe Function and Performance Monitoring following Total Sleep Deprivation
Renn, Ryan
Imaging studies have shown reduced frontal lobe resources following total sleep
deprivation (TSD). The anterior cingulate cortex (ACC) in the frontal region plays a role
in performance monitoring and cognitive control; both error detection and response
inhibition are impaired following sleep loss. Event-related potentials (ERPs) are an
electrophysiological tool used to index the brain's response to stimuli and information
processing. In the Flanker task, the error-related negativity (ERN) and error positivity
(Pe) ERPs are elicited after erroneous button presses. In a Go/NoGo task, NoGo-N2 and
NoGo-P3 ERPs are elicited during high conflict stimulus processing. Research
investigating the impact of sleep loss on ERPs during performance monitoring is
equivocal, possibly due to task differences, sample size differences and varying degrees
of sleep loss. Based on the effects of sleep loss on frontal function and prior research, it
was expected that the sleep deprivation group would have lower accuracy, slower
reaction time and impaired remediation on performance monitoring tasks, along with
attenuated and delayed stimulus- and response-locked ERPs.
In the current study, 49 young adults (24 male) were screened to be healthy good
sleepers and then randomly assigned to a sleep deprived (n = 24) or rested control (n =
25) group. Participants slept in the laboratory on a baseline night, followed by a second
night of sleep or wake. Flanker and Go/NoGo tasks were administered in a battery at
1O:30am (i.e., 27 hours awake for the sleep deprivation group) to measure performance
monitoring. On the Flanker task, the sleep deprivation group was significantly slower
than controls (p's <.05), but groups did not differ on accuracy. No group differences were
observed in post-error slowing, but a trend was observed for less remedial accuracy in the
sleep deprived group compared to controls (p = .09), suggesting impairment in the ability to take remedial action following TSD. Delayed P300s were observed in the sleep
deprived group on congruent and incongruent Flanker trials combined (p = .001). On the
Go/NoGo task, the hit rate (i.e., Go accuracy) was significantly lower in the sleep
deprived group compared to controls (p <.001), but no differences were found on false
alarm rates (i.e., NoGo Accuracy). For the sleep deprived group, the Go-P3 was
significantly smaller (p = .045) and there was a trend for a smaller NoGo-N2 compared to
controls (p = .08). The ERN amplitude was reduced in the TSD group compared to
controls in both the Flanker and Go/NoGo tasks. Error rate was significantly correlated
with the amplitude of response-locked ERNs in control (r = -.55, p=.005) and sleep
deprived groups (r = -.46, p = .021); error rate was also correlated with Pe amplitude in
controls (r = .46, p=.022) and a trend was found in the sleep deprived participants (r =
.39, p =. 052). An exploratory analysis showed significantly larger Pe mean amplitudes (p
= .025) in the sleep deprived group compared to controls for participants who made more
than 40+ errors on the Flanker task.
Altered stimulus processing as indexed by delayed P3 latency during the Flanker
task and smaller amplitude Go-P3s during the Go/NoGo task indicate impairment in
stimulus evaluation and / or context updating during frontal lobe tasks. ERN and NoGoN2
reductions in the sleep deprived group confirm impairments in the monitoring system.
These data add to a body of evidence showing that the frontal brain region is particularly
vulnerable to sleep loss. Understanding the neural basis of these deficits in performance
monitoring abilities is particularly important for our increasingly sleep deprived society
and for safety and productivity in situations like driving and sustained operations.
Tue, 07 May 2013 00:00:00 GMThttp://hdl.handle.net/10464/43602013-05-07T00:00:00Z